How to Check Water Quality Before You Swim in England

Last checked: 23 September 2026. Classifications are updated each winter and alert services change, so follow the links to the live sources before you swim.

A beach can hold an Excellent rating and still be a bad idea the morning after a thunderstorm. Checking water quality in England means reading three kinds of information together:

• The long-term rating, which tells you how clean a spot usually is.
• Daily forecasts and alerts, which tell you about risk right now.
• Your own read of the weather, especially recent heavy rain.

Here is how each one works and where to find it.

Start with the bathing water classification

A designated bathing water is a beach or inland spot officially recognised because lots of people swim there. England had 451 in 2025, and 13 new sites were added for the 2026 season. The Environment Agency (EA) samples them through the bathing season.

The EA tests for two bacteria, E. coli and intestinal enterococci. They show whether there are germs in the water that could make you ill. Results from the last four seasons produce each site's annual classification:

• Excellent: the highest, cleanest class.
• Good: generally good water quality.
• Sufficient: meets the minimum standard.
• Poor: has not met the minimum standard.

Councils must display the classification on a sign at each bathing water during the season. At a Poor site, the sign must include the "advice against bathing" symbol and information on the causes of pollution.

How England did in 2025. The EA measured 449 of the 451 bathing waters (two couldn't be sampled because of access problems). Of these, 297 (66.1%) were Excellent and 417 (92.9%) met at least the minimum standard. 32 (7.1%) were rated Poor. The 2026 results are provisionally due on 15 December 2026.

2025 ratings for some well-known swims

Source: the EA's 2025 individual classification results. A rating covers the named bathing water, which may not match every stretch of a beach or river.

The catch. A classification is a four-year average. It tells you what's typical, not what's in the water today. Even an Excellent beach can dip after heavy rain.

The bathing season, and why it matters

Current government guidance puts the bathing season at 15 May to 30 September. That's when the EA samples, when forecasts run and when councils must put up signs.

Outside those dates, the EA's seasonal sampling and pollution risk forecasts stop. Some venues run their own winter tests; the Hampstead Heath ponds, for example, are tested fortnightly from October to April. The Safer Seas & Rivers Service marks many sites "out of season". In winter, lean more on overflow maps and your own judgement.

The government announced reforms to the bathing water rules in 2025, including more flexible seasons. For now, guidance still gives 15 May to 30 September, so check the latest before relying on it.

Check the day: pollution risk forecasts

During the season, the EA publishes daily pollution risk forecasts for a number of bathing waters. These flag days when water quality may drop for a while. Heavy rainfall is the usual trigger, but wind, sunlight and tide can play a part.

When a risk is forecast, the EA advises against bathing and posts that advice on Swimfo, its bathing water website. Many beaches also show it on signs.

The EA is clear that a forecast is not the same as a confirmed pollution event. The system uses historical data to predict when pollution is likely. Treat it as a strong "not today" rather than proof the water is dirty.

Swimfo also shows the latest sample results. At the beach, councils must post notices about pollution incidents, including rare "abnormal situations" expected no more than once every four years on average.

Sewage alerts: Surfers Against Sewage

The Safer Seas & Rivers Service from Surfers Against Sewage (SAS) is a free app and website. It covers more than 850 UK locations and pulls water company data and official forecasts into one map.

What its symbols mean:

• Sewage alert. A confirmed sewage discharge near this spot may reduce water quality. The alert stays up while the discharge runs and for 48 hours after it stops.
• Pollution risk forecast. Bathing isn't advised because a drop in quality is forecast. Only available in the bathing season.
• Poor annual classification. A permanent alert. Bathing isn't advised.
• Pollution incident. A confirmed incident, such as an oil spill, burst sewer or algae bloom.
• No alert. Data is coming in with no sign of reduced quality.
• Out of season, Maintenance or Dormant. No live information right now. Don't read these as "clean".

SAS also runs a Live Sewage Map covering more than 18,000 overflows across the UK. It shows where overflows are discharging now. SAS points out that a discharge alone doesn't tell you whether a nearby swim spot is affected. England is the only UK nation where every combined sewer overflow must legally be monitored, so all of them appear on the map.

Water company storm overflow maps

When heavy rain overwhelms the sewers, storm overflows release a mix of rainwater and untreated sewage into rivers and the sea. Since 1 January 2025, water companies in England must publish when an overflow starts discharging, and where, within an hour. They must also publish when it stops.

The information has to be readily accessible to the public. Thames Water, for example, runs a storm discharge map showing overflows discharging now and the time and length of the last recorded discharge. Look on your local water company's website for its equivalent.

Read these maps with care. Thames Water says its monitors can be set off by something as small as a weed. So an alert shows a likely discharge, not a confirmed one. Equally, a quiet map doesn't mean the water is safe to swim in.

A practical way to use them: look for active or recent discharges upstream of a river spot, or close to a beach. If you find one, go somewhere else.

Rivers and lakes need extra care

Most rivers and lakes are not designated bathing waters. UK Health Security Agency (UKHSA) guidance notes that these are managed to protect fish and wildlife, not people. Nobody tests them for the bacteria used to judge bathing water. They can carry sewage, livestock waste or farm and industrial pollution.

More river sites are being designated, though. New inland bathing waters for 2026 include Ham and Kingston on the River Thames, Pangbourne Meadow, and Swale above Richmond Falls.

In fresh water, look out for blue-green algae too. UKHSA says you can't tell from looking whether a bloom or scum is toxic, and the toxins can seriously harm pets. Stay out, and keep dogs away.

Rainfall rules of thumb

No official rule sets how long to wait after rain. The Outdoor Swimming Society says there is no set time, because rivers vary so much. These habits help:

• Treat heavy rain as a red flag, especially after a long dry spell. Rain washes bacteria off farmland, roads and towns, and can trigger overflows.
• Check alerts again on the day. That's SAS's own advice. Conditions can change overnight.
• In rivers, wait for the level to drop. High, fast, brown water brings pollution, debris and stronger currents.
• Avoid swimming just downstream of sewage works or overflows after rain.
• On beaches, keep away from stream water running across the sand.
• Use the 48-hour window as a minimum, not a guarantee. SAS keeps sewage alerts up for 48 hours after a discharge ends. Water can take longer to clear.

SwimPass spot pages show a live SwimScore for conditions such as wind, waves and temperature. It isn't a water quality check, so pair it with the sources above.

If you swam after heavy rain

Most illness from open water is mild, but some infections are serious. UKHSA advice:

• Straight after: wash your hands well with soap and water before eating, and clean any cuts or grazes.
• Wetsuit: rinse it in clean water as soon as you can, then wash your hands after handling it.
• If you feel unwell: seek medical help and say you've been swimming in open water. SAS suggests your doctor, a pharmacist or NHS 111.
• Before your next swim: wait until you've had no diarrhoea for at least 48 hours, or longer if your doctor advises.

If you see pollution, report it to the Environment Agency's 24-hour incident hotline on 0800 80 70 60. SAS also collects reports from people who fell ill after swimming.

A two-minute check before you swim

1. Look up the spot on Swimfo. Is it a designated bathing water, and what is its rating?
2. In season, check for a pollution risk forecast or advice against bathing.
3. Open the Safer Seas & Rivers Service for sewage alerts at or near the spot.
4. For rivers, check the water company's overflow map upstream.
5. Think about the last 48 hours of rain, and look at the water when you arrive.
6. Check the live SwimScore for the conditions.

Wales, Scotland and Northern Ireland run their own bathing water services. GOV.UK links to each one. For places to swim, browse our UK swim spots, or read our guides to the Hampstead Heath ponds and London's lidos.

Sources

• Check the quality of beach and bathing water in England – GOV.UK
• Bathing water quality statistics – GOV.UK
• 2025 statistics on English coastal and inland bathing waters – Defra/Environment Agency
• National bathing waters in England for 2025: individual classifications (ODS) – Environment Agency
• Bathing water quality statistics – England (2026) release announcement – GOV.UK
• Bathing waters: list of designated waters in England – GOV.UK
• Bathing waters: apply to designate or de-designate – GOV.UK
• Bathing water information and signage rules for local councils – GOV.UK
• Bathing waters collection – GOV.UK
• Bathing water reforms keep pace with Britain's love of swimming – Defra
• Bathing water season in England begins as applications re-open – Environment Agency
• 'Swimfo' helps people choose where and when to swim – Environment Agency
• Swimfo – Environment Agency
• Swim healthy – UKHSA and Environment Agency
• Storm overflows: policy and guidance – Defra
• Storm discharge and event duration monitoring – Thames Water
• UK Live Sewage Map and Safer Seas & Rivers Service – Surfers Against Sewage Data HQ
• Safer Seas & Rivers Service – Surfers Against Sewage Data HQ
• What happens if you swim in sewage water? – Surfers Against Sewage
• Check Before You Go – Surfers Against Sewage
• Understanding wind and rain – The Outdoor Swimming Society
• Report an environmental problem – GOV.UK